As long as you buy your fuel at a reputable truck stop you shouldn't need any kind of additive during the warmer months, in extremely cold conditons an anti-gel might be needed, but only if the coach was to set outside for an (not running) extended period of time in sub zero weather. I also try not to fuel when a tanker is unloading to underground tanks as that will stir up any water/condensation that has settled to the bottom of the tank.
